1. Field of the Disclosure
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a LCD device including a polymer wall for maintaining a cell gap.
2. Discussion of the Related Art
Owing to advantages such as good portability and low power consumption by low operating voltage, a liquid crystal display (LCD) device is widely used in various fields of notebook computer, monitor, spacecraft, aircraft, and etc.
The LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the lower and upper substrates.
Recently, there is an increasing interest in flexible LCD device based on a flexible plastic substrate. The flexible LCD device is a rollable or windable device, which is paperlike, whereby the flexible LCD device enables easy keeping and good portability. Owing to these advantages, the flexible display device has been steadily studied and developed as a next-generation display device.
However, when curving or bending the flexible LCD device, it may have a problem related with non-uniformity in cell gap between the lower and upper substrates. In order to overcome this problem of non-uniformity in cell gap, there has been proposed a method of applying a polymer wall between the lower and upper substrates.
Hereinafter, a related art LCD device including a polymer wall will be described as follows.
FIG. 1A is a perspective view of a related art LCD device. FIG. 1B is a cross sectional view of the related art LCD device.
As shown in FIG. 1A, the related art LCD device includes a lower substrate 10, an upper substrate 20, polymer walls 30, and a liquid crystal 40.
The lower substrate 10 is arranged below the upper substrate 20, and the polymer walls 30 are formed in a matrix configuration between the lower substrate 10 and upper substrate 20. Also, the liquid crystal 40 is provided in a space between each of the polymer walls 30. Thus, even though the related art LCD device is repeatedly curved or bent, a cell gap between the lower substrate 10 and upper substrate 20 is uniformly maintained owing to the polymer walls 30.
The related art LCD device may be manufactured by processes of bonding the lower substrate 10 and upper substrate 20 to each other while providing a mixture of ultraviolet (UV)-curable compound and liquid crystal 40, and forming the polymer wall 30 having a desired shape by irradiating the UV-curable compound with UV light. According to the irradiation of UV light, the UV-curable compound is cured with a phase separation from the liquid crystal 40. Also, the liquid crystal 40 is positioned between each of the polymer walls 30. The polymer wall 30 will be described in detail with reference to FIG. 1B.
As shown in FIG. 1B, lines 12 are formed on the lower substrate 10 of the related art LCD device, and a passivation layer 14 is formed on the lines 12. On the upper substrate 20 of the related art LCD device, there are light-shielding layers 22, a color filter layer 24 between each of the light-shielding layers 22, and an overcoat layer 26 on the color filter layer 24. Also, the polymer walls 30 are formed between the lower substrate 10 and upper substrate 20, and the liquid crystal 40 is provided in the space between each of the polymer walls 30.
As described above, the polymer wall 30 is formed by irradiating the UV-curable compound with UV light. Thus, in order to form the polymer wall 30, the lower surface of the lower substrate 10 or the upper surface of the upper substrate 20 has to be irradiated with UV light.
However, the light-shielding layer 22 and color filter layer 24 formed on the upper substrate 20 have a low transmittance of UV light. Thus, if the upper surface of the upper substrate 20 is irradiated with UV light, it is difficult to form the polymer wall 30. Meanwhile, in case of a COT (color filter on TFT) structure in which the color filter is formed on the lower substrate 10, the polymer wall 30 may be formed by irradiating the upper surface of the upper substrate 20 with UV light. In this case, the structure of the LCD device is limited only to the COT structure.
For manufacturing various structures of a LCD device, the polymer wall 30 has to be formed by a UV irradiation onto the lower surface of the lower substrate 10. That is, as shown in the drawings, a mask 50 including a transparent portion 50a and a non-transparent portion 50b is positioned below the lower substrate 10, and then a UV irradiation is performed in such a manner that UV light is emitted from the lower side of the mask 50 to the lower surface of the lower substrate 10. Accordingly, the UV-curable compound is irradiated with UV light penetrating through the transparent portion 50a, thereby forming the polymer wall 30. In this case, the polymer wall 30 is formed in the same pattern as that of the transparent portion 50a of the mask 50.
In this case, the lines 12, such as gate lines or data lines, are formed on the lower substrate 10, and the UV light cannot penetrate through the lines 12. Accordingly, the transmission part 50a of the mask 50 is positioned to correspond with the other regions except the lines 12. As a result, the polymer wall 30 is formed in the other regions except the lines 12, that is, they are formed in a pixel region for displaying an image. Because the polymer wall 30 is formed in the pixel region for displaying an image, light transmittance of the LCD device is lowered, and thus luminance is also deteriorated.